Best suited material...suggestions???? 1

[crowellmachine]

Hi All,

New here...My application is: reaching into a moving belt
furnace with fully automated robotic arm, to pick up a
powdered metal part, and place it in a forging die. The
temperature in the oven is approx. 1600f. It is a continous
operation with aprox. a 7 sec. cycle time(trying to show
heat environment, hot, cold etc. in,out) Robot arm frame
is water cooled, but hardware is not. The part in question
is the actuating rod. Previous materials have been 304, 316, and 625..Trying 330 right now..Cost and availibility
a problem with 625. A 1 inch square nut with a .500 hole thru, gets welded to the .500x26" rod, welding with stick
(308 rod)right now trying 304 nut, and 330 rod. Stress
relieving after weld @650f, for 2 hours, then turn furnace off and cool down with the furnace. Eventually part fails
(cracks or completely breaks in half,always at weld)
Usage is constant, and would like to help customer by
addressing the problem...Any suggestions from you guys would be greatly appreciated....KJC

 

[metengr]

After reviewing your post, I would say that the reason you are having the weld failure in this application is the selection of the 308 filler metal. Most likely, you are probably forming sigma phase in the 308 weld deposit over time at exposure to temperatures above 1200 deg F. The formation of sigma phase results in the loss of ductility and toughness of the weld deposit, which makes it prone to thermal fatigue crack propagation.

I would stick with the 330 ss actuating rod, and use Inconel 182 filler metal to join the 304 ss nut to the 330 ss rod instead of 308 filler metal. The 330 ss normally exhibits high resistance to thermal shock. The higher nickel and chromium content will provide increased oxidation and creep strength. Inconel 182 is a nickel base electrode (SFA 5.11 ENiCrFe-3) with excellent ductility, and will handle the thermal stresses with no problem.

No stress relief is required after welding.

 

[arunmrao]

Apart from mcguire's recommendation you can replace the 304 nut too. From 330 rod get a nut made so that compatibility improves. If this is not possible explore the possibility of 310 nut, material for which is more easily available. 870C is cool temperature for these alloys

 

[crowellmachine]

Does this mean that 304 itself has a high enough heat range to be used in this application? ,If i can get the weld situation figured out???? Thx. KJC

 

[EdStainless]

As long as the stresses are low enough the 304 should work.
Once you get the weld straigntened out your next failure will probably be realted to thermal fatigue.
Then you can start trying to get people to accept that you need to go to Ni based materials. Without going crazy Alloy X may be your best option.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[rolledalloy]

Welding of RA330 can be tricky. Use of a stainless filler like 308 to weld it to 304 is a bad idea. RA330 is fully austenitic and is sensitive to weld solidification cracking as it is. 308 filler relies on ferrite in the weld to prevent cracking. Dilution with the 35% nickel RA330 base metal will drastically reduce the ferrite content of the weld. These small cracks can open up in service if not detected. 182 is a good option or RA330-04 filler would also work for this joint. RA330-04 fillers have high manganese which reduces the tendency of the welds to crack during solidification.

RA330 hex nuts are available from Rolled Alloys as is threaded bar if that helps.

Other issue is 304 expands more than RA330 at 1600F. 304 expands roughly 10% more on each cycle. That can induce additional stresses that lead to cracking.

If an all RA330 welded with RA330-04 does not do the trick then I would suggest looking at alloy 600 welded with 182 rod or 82 wire. Alloy 600, like RA330, will not embrittle from sigma phase so it retains its ductility and it has an even lower coefficient of expansion than RA330 roughly 7% less.

Weld penetration is likely poor in this design. Nickel alloys are difficult to get good penetration when welding. You may look at how you might get a better weld joint if possible in your design to improve the life of the component.

 

[MikeHalloran]

I know it seems wasteful at first glance, but did you get a quote on machining the part in one piece from 1-1/2" round?




Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA

 

[crowellmachine]

ATTN: Rolled Alloys,

I previously have used 600 series material (which was purchased from you). However price and availibility are
not what they used to be.( I realize that this is out of your control) My customer has asked me to
experiment with other materials, so that the price can stay where it is. I was previously using 625RA. This robot cycles 25,000 times a day. there are 22 of them. I will
heed your advice and go from here. Thank you for the very informative post!! KJC

Crowell Machine
Emporium, PA